The invention relates to show cases for keeping and for exhibiting objects, the sides, the bottom and the cover construction of which encompass the interior of the show case more or less hermetically in order to protect said objects against dust and environmental loads of all kind. No matter how good and nearly perfect a show case may be sealed, it must be expected in practice that, due to variations of air pressure and temperature in the show case and in its ambient atmosphere, air and also dust reach the interior of the show case. Especially in case of air pressure variations occurring when high and low barometric pressure conditions alternate, each show case "inhales" up to 1/10th of its volume.
In order to protect the objects in show cases against ambient temperature variations or in order to maintain a predetermined temperature inside the show cases, it is general practice to provide show cases with an air conditioning system. However, such equipment is, on the one hand, very expensive and pays only for very expensive exhibits, and, on the other hand, they do not prevent harmful gases from entering the interior of the show cases together with air and from attacking the exhibits. Furthermore, it has turned out that strong air flows depending on the system may affect some objects detrimentally. Moreover, show cases connected to such air conditioning systems must be stationarily installed - usually along walls. Also such air conditioning systems can cause great damage in case of malfunction.